Current Issue

Bug of the Week is written by "The Bug Guy," Michael J. Raupp, Professor of Entomology at the University of Maryland.

Bumble bee, carpenter bee, he bee, she bee: Bumbus spp., Xylocopa spp.

 

On a dewy morning, male (left) and female (right) carpenter bees await a warm-up from the brilliant autumn sun.

 

You may have seen the carpenter bee’s hole on the outside of your siding - here’s a look at the brood galleries on the inside.

In this season of record breaking, smoking hot days, blossoms have been humming with a multitude of bees, butterflies, and other fascinating pollinators. Visits to flower beds and pollinator gardens with children and adults during the past week or two, sparked wonder at the vast number of large bumble bees busily gathering nectar from late season blossoms. While there is no doubt that many of the bee sightings were indeed bumble bees, this is the season that a fresh crop of carpenter bees mobs patches of flowers to fatten-up on floral delights in preparation for the upcoming winter. Months ago busy female carpenter bees devoted weeks constructing galleries in wood, provisioning these galleries with pollen, and depositing eggs within. Summer and early fall were a time for the eggs to hatch and the young bee larvae to consume these morsels, complete their development, pupate, and emerge as adults.  Galleries used as nurseries throughout spring and summer will soon serve as winter refuges for this year’s class of carpenter bees.

Note the shiny hairless abdomen of the carpenter bee.

With a little practice, carpenter bees can be distinguished from their look-alike bumble bee cousins. A carpenter bee’s rump is relatively naked, whereas a bumble bee’s rear end is usually quite well cloaked with hair. The head of the carpenter bee is about the width of the thorax, the body segment just behind the head. The head of a bumble bee is noticeably smaller than thorax.

Hair on the abdomen is a hallmark of the bumble bee.

Having identified the bee as a carpenter bee, how does one distinguish the guys from the gals? The gender of some carpenter bees, such as the Large Carpenter bee, Xylocopa virginica, are easily recognized by the presence or absence of a large creamy white patch just below the antennae on the front of its face: the male sports the white patch, but the face of the female large carpenter bee is entirely black. On occasion I have captured large male carpenter bees with my hand to demonstrate that they are not to be feared, as they have no stinger - only female bees are equipped with this notable appendage. On one occasion I mistakenly grabbed a female carpenter bee and learned the awesome power of this appendage. If for some strange reason you choose to handle large carpenter bees, please be certain that they are indeed carpenter bees and not bumble bees, and only handle the he bee and not the she bee.

Bumble bees have a hairy abdomen, carpenter bees do not. The male carpenter bee has a white patch on his face and the female’s face is entirely black. A male foraged on a lower blossom until he spotted a female foraging just above, and then both appeared to have other business on their minds as they raced away.

Another observation regarding behaviors of carpenter bees and bumble bees comes at the close of the work day. Industrious bumble bee workers usually return to their nest at dusk with the final loads of nectar and pollen to fatten-up any future queens and drones that might still be developing in the nest. But unlike bumble bees, with the approach of nightfall large carpenter bees often remain behind on blossoms to snooze. With no nest to provision or hungry future royals to feed, it is no surprise to find sleepy carpenters resting on flowers in the early light of dewy autumn mornings. One of their favorite resting spots in my garden is a patch of catmint. Members of the mint family are renowned for their ability to attract a variety of pollinating insects, in addition to their medicinal qualities. Perhaps, the lazy behavior of my carpenter bees is related not only to the nighttime chill that cools their bodies, but also to some soporific chemical found in the nectar of mint. Who knows?

When the killing frost finally puts an end to my autumn bloomers, the last of the carpenter bees will enter their vacated brood galleries, not to return until next spring. On a cool autumn morning, take an early trip to the garden to visit the newly minted class of 2019 carpenter bees. 

Acknowledgements

Bug of the Week thanks MPT, University of Maryland Master Gardeners, and the Howard Conservancy for providing the inspiration for this episode. The really cool bee book “The Bees in Your Backyard: A Guide to North America’s Bees” by J. S. Wilson and O.M. Carril was used as a resource for this episode.